The present invention relates to adhesive dispensing systems and, in particular, to adhesive application systems for applying a bead of an adhesive to each of a series of blanks moving transverse to the direction of adhesive application.
Many commercial processes produce products from blanks of a foldable material, such as paper or a thin cardboard, in a multi-station automated process. To create structures such as pockets, portions of the blanks, such as flaps, are glued with a straight-line gluer and subsequently folded in a manner to form the pocket. To that end, a series of blanks are conveyed past one or more spaced-apart adhesive applicators of the straight-line gluer. One or more glue beads are applied to each blank in a direction generally aligned with its direction of travel in the gluer or the machine direction. Each blank makes a single pass through the straight-line gluer so that all glue beads are applied simultaneously.
One conventional method of creating a pocket from a generally rectangular blank 5 is diagrammatically illustrated in FIG. 1. To facilitate this method, the blank 5 is die cut as a rectangular sheet with an integral flap 5a provided on a leading edge. In this method, a straight-line gluer applies two parallel adhesive beads 6a,b to the flap 5a that are aligned parallel to a machine direction (MD) and positioned near opposite side edges of the flap 5a. After the adhesive beads 6a,b are applied, the flap 5a is folded over the blank 5 at a fold line 5b and adhesively bonded thereto along the lines of contact with the adhesive beads 6a,b to form the pocket. The fold line 5b creates a bottom seam for the pocket. However, the folding step of this conventional process is time-consuming and inefficient because several inches of the flap 5a must be guided into a back-fold device and folded in an 180xc2x0 arc relative to fold line 5b to contact the blank 5.
Another conventional method of forming a pocket from a blank 7 is diagrammatically illustrated in FIG. 2. In this method, the blank 7 is die cut with an integral flap 7a extending from a side edge. A straight-line gluer applies a bead of adhesive 8a near the side edge of the flap 7a that is aligned parallel to a machine direction (MD) for purposes of creating a side seam. Another bead of adhesive 8b is manually applied by hand to the flap 7a in a direction transverse to the machine direction. The integral flap 7a is then folded over the blank 7 to adhesively bond along the adhesive beads 8a, 8b for forming a pocket. However, this conventional process is time-consuming because of the necessity of applying the transverse bead 8b of adhesive by hand.
Blanks are typically formed by a die cutting operation that generates significant quantities of waste paper. The ability of conventional straight-line gluers to only apply beads of adhesive in a direction parallel to the machine direction dictates the geometrical configuration or shape of the blanks. The die cutting operation to geometrically shape blanks for the conventional gluing method of FIG. 2 generates excessive amounts of trimmed material. This trimmed material or scrap material produces a waste stream that must be either recycled or discarded.
Thus, a gluer is needed that can rapidly apply a bead of adhesive in an application direction transverse to the machine direction as the blank is conveyed past the adhesive applicators.
According to the present invention, a dispensing system is provided for applying a transverse bead of an adhesive to a blank being conveyed past a coating head in a first direction on a conveyor. The dispensing system comprises a coating head capable of applying the bead of the adhesive to the blank and a mounting assembly mounted to the conveyor. The mounting assembly orients the coating head in a second direction that is substantially transverse or orthogonal to the first direction for applying the bead of the adhesive transversely to the first direction.
In certain embodiments, the dispensing system is constructed and arranged such that the coating head can be moved vertically over a range of movement relative to a plane containing the blank. In other embodiments, the dispensing system is constructed and arranged such that the coating head can be rolled about the machine direction over a range of angular movement relative to the first direction. In still other embodiments, the dispensing system is constructed and arranged such that the coating head can be angularly pitched transverse to the machine direction over a range of angular movement relative to the first direction. These two degrees of rotational freedom and degree of translational freedom are utilized individually, or in combination, for positioning the coating head relative to the blank.
In certain embodiments, the dispensing system may include a pattern controller for regulating the application of adhesive from the coating head to a surface of the blank. The dispensing system may further include a photosensor for detecting an edge of the blank and providing a signal to the pattern controller for use in triggering the application of adhesive from the coating head to the blank. A bifurcated fiber optic may be interfaced with the photosensor which has an emitter aperture and a receiver aperture aligned with the emitter aperture so that the photosensor operates in an opposed sensing mode.
The present invention drastically reduces the waste of foldable material from the die cutting process because the blanks need not be die cut with an integral side flap that depends from a side edge. Instead, such blanks may be die cut with an integral flap that depends from an end edge. This difference dramatically reduces the trim generated by the die cutting operation to prepare blanks suitable for use with the present invention compared with die cutting to prepare blanks suitable for conventional straight-line gluers.
The dispensing system may include a lower bracket disposed upstream from the coating head for applying an upward force against the blank. In one embodiment, the lower bracket includes a reduced friction strip positioned adjacent to the coating head and in contact with the blank for reducing the incidence of blank buckling.
The present invention also eliminates the need to rely on a back-fold device or a manual folding operation for folding the flap to form the pocket. Furthermore, the right angle glue of the present invention applies the transverse adhesive bead in a fully automated manner. By eliminating the conventional manual application of the transverse adhesive bead, the pocket-forming process is accelerated so that productivity is enhanced and blank throughput is improved. In addition, the right angle glue of the present invention provides standardized, accurate, consistent, reproducible and reliable adhesive application that represents an improvement over manual application of the transverse bead.